The present invention relates to a method of controlling an automotive powertrain and in particular to using a selectively actuatable one-way clutch to enter and exit a parallel mode of operation for a powersplit powertrain.
An automotive vehicle may use a powersplit hybrid electric powertrain. Included in the powersplit powertrain is an electric generator, which may also alternatively operate as an electric motor. The powersplit powertrain may be operated in a plurality of modes, including negative powersplit, positive powersplit, and parallel modes. In the positive powersplit mode the generator operates and produces electrical power. In the negative powersplit mode the generator consumes electrical power and produces a torque to propel the vehicle. In the parallel mode the generator neither produces nor consumes electrical power, which allows the vehicle to be propelled by a combined torque produced by the engine, a second electric motor, and braking of the generator. Typically, a friction clutch is used to brake the generator so that the powertrain may enter the parallel mode.
However, time required to brake the generator to enter the parallel mode reduces fuel efficiency for the powersplit powertrain. The friction clutch may require a hydraulic system with a pump to maintain pressure to keep the friction clutch braking the generator. The pump creates an additional load on the powertrain and may further reduce fuel efficiency.